Field of the Invention
The present invention relates to a battery pack for an electric power tool that is detachably mounted on a tool body of the electric power tool as a power source for the electric power tool.
Description of the Related Art
A battery pack for an electric power tool, which is detachably mounted on a tool body as a power source, has been used in electric power tools. A user can conveniently use an electric power tool when the battery pack for the electric power tool is mounted on the tool body. The battery pack for an electric power tool generally includes a case that serves as a housing as well as forming an outer package, and a battery body that is provided in the case. The case is generally formed by combining an upper and a lower case. Further, the battery body includes a plurality of battery cells that can be charged and discharged and a circuit board that controls the charging and discharging of the plurality of battery cells. The plurality of battery cells are generally held in the case by a support structure that is called a cell holder (for example, refer to Japanese Laid-Open Patent Publication No. 2008-10315). One end of an electrode member is connected to an electrode of the battery cell, which is held by the cell holder, typically using welding or the like. Current is allowed to flow via the electrode members. The opposite end of the electrode member is connected to the circuit board, which is supported by the cell holder, typically using welding or the like.
The above-mentioned battery cell is the heaviest component among those of the battery pack for an electric power tool. Because of this, natural vibration of the battery cell is different from that of other battery pack components. For this reason, when impact or vibration is applied to the battery pack from the outside, the movement of the battery cell and the electrode member connected to the electrode of the battery cell may become different from each other. Since this movement for causing the difference results in a force being applied to the connected portion, it is desirable that this movement be reduced as much as possible. In the above-mentioned Japanese Laid-Open Patent Publication No. 2008-10315, a member serving as a cushion is inserted between the case and the battery cells in the battery pack. However, this member does not serve to fix the battery cells to the case. For this reason, the movement of the battery cells relative to the electrode members connected to the above-mentioned electrodes is not suppressed.
Thus, there is a need in the art to provide an improved battery pack for an electric power tool that is detachably mounted on a tool body of the electric power tool as a power source of the electric power tool. Such a battery pack suppresses the movement of battery cells relative to a case or the movement of the battery cells relative to a cell holder when impact or vibration is applied to the battery pack for an electric power tool from the outside.